Endocrine Abstracts

Background, case-history: Hypercalcaemia secondary to parathyroid hormone (PTH) independent mechanisms is well known, with differentials including Sarcoidosis. We describe a case of Sarcoid Myositis presenting with symptomatic hypercalcaemia (adjusted serum calcium levels of 3.12 mmol/l) but no muscle weakness in a 39-year-old lady with a background of Type 1 Diabetes Mellitus, Hyperthyroidism, and Rheumatoid Arthritis.

Investigations: Laboratory investigations comprised of suppressed PTH, vastly elevated Calcitriol (1,25-dihydroxy vitamin D) level (314pmol/l, normal 55-139pmol/l) along with normal CT scan thorax, abdomen, and pelvis. Serum calcium was refractory to fluid resuscitation and intravenous pamidronate, thus other rare differentials were considered. Full biochemical and immunological investigations revealed serum ACE levels above the detectable range (>148 U/l) suggestive of sarcoidosis. As chest findings and CT scan reports were unremarkable, an extra-pulmonary cause of sarcoidosis was considered. Subsequently, an FDG PET CT scan showed increased muscular uptake in gluteal muscles suggestive of inflammatory myositis; heightening the suspicion of rarely reported, and often asymptomatic, Sarcoid myositis.

Results, treatment: Biopsy from the inflamed site, localized from MRI, showed prominent granulomatous inflammation typical of sarcoid myositis. Our patient was commenced on a reducing dose of steroids, which normalised adjusted serum calcium. Disease-modifying therapy included Rituximab, targeting B cells numerous within granulomas.

Conclusions: points for discussion: Granulomatous causes, especially in PTH independent cases of hypercalcaemia should be considered as a part of differential diagnosis at initial presentation and relevant laboratory workups should be incorporated in the investigative protocols. Sarcoidosis accounts for calcitriol-mediated hypercalcaemia in 49% of cases, other causes include haematological malignancy (17%) and infection (8%). Therefore, in cases of hypercalcaemia of unknown origin, calcitriol levels can help form a focused differential diagnosis. The manifestation of sarcoidosis with myositis only is rare, cases are usually accompanied by other manifestations with myopathy often being chronic and asymptomatic in 86% of patients.